Check for unstable types in IPC messages.

tools/clang/plugins/CMakeLists.txt

 set(plugin_sources
   ChromeClassTester.cpp
   FindBadConstructsAction.cpp
-  FindBadConstructsConsumer.cpp)
+  FindBadConstructsConsumer.cpp
+  CheckIPCVisitor.cpp)
 
 if(WIN32)
   # Clang doesn't support loadable modules on Windows. Unfortunately, building
   # the plugin as a static library and linking clang against it doesn't work.
   # Since clang doesn't reference any symbols in our static library, the linker
   # strips it out completely.
   # Instead, we rely on the fact that the SOURCES property of a target is no
   # read-only after CMake 3.1 and use it to compile the plugin directly into
   # clang...
   cmake_minimum_required(VERSION 3.1)
@@ skipping 13 matching lines @@
   add_dependencies(libFindBadConstructs clang)
 
   cr_install(TARGETS libFindBadConstructs LIBRARY DESTINATION lib)
 
   cr_add_test(plugins_test
     python tests/test.py
     ${CMAKE_BINARY_DIR}/bin/clang
     $<TARGET_FILE:libFindBadConstructs>
     )
 endif()